Method of contact printing on gold coated films

ABSTRACT

The present invention comprises methods of contact printing of patterned, self-assembling monolayers of alkanethiolates, carboxylic acids, hydroxamic acids, and phosphonic acids on metallized thermoplastic films, the compositions produced thereby, and the use of these compositions. Patterned self-assembling monolayers allow for the controlled placement of fluids thereon which contain a chemically reactive, indicator functionality. The optical sensing devices produced thereby when the film is exposed to an analyte and light, can produce optical diffraction patterns which differ depending on the reaction of the self-assembling monolayer with the analyte of interest. The light can be in the visible spectrum, and be either reflected from the film, or transmitted through it, and the analyte can be any compound reacting with the fluid on the self-assembling monolayer. The present invention also provides a flexible support for a self-assembling monolayer on gold or another suitable metal.

TECHNICAL FIELD

The present invention is in the field of contact printing and, morespecifically the present invention is in the field of microcontactprinting on metal films such as gold.

BACKGROUND OF THE INVENTION

Microcontact printing is a technique for forming patterns of organicmonolayers with μm and submicron lateral dimensions. It offersexperimental simplicity and flexibility in forming certain types ofpatterns. It relies on the remarkable ability of self-assembledmonolayers of long-chain alkanethiolates to form on gold and othermetals. These patterns can act as nanometer resists by protecting thesupporting metal from corrosion by appropriately formulated etchants,or, can allow for the selective placement of fluids on hydrophilicregions of the pattern. Patterns of self-assembled monolayers havingdimensions that can be less than 1 μm are formed by using thealkanethiol as an "ink", and by printing them on the metal support usingan elastomeric "stamp". The stamp is fabricated by molding a siliconeelastomer using a master prepared by optical or X-ray microlithographyor by other techniques.

Microcontact printing of patterned self-assembled monolayers brings tomicrofabrication a number of new capabilities. First, microcontactprinting makes it possible to form patterns that are distinguished onlyby their constituent functional groups; this capability permits thecontrol of surface properties such as interfacial free energies withgreat precision. Second, because microcontact printing relies onmolecular self-assembly, it generates a system that is (at leastlocally) close to a thermodynamic minimum and is intrinsicallydefect-rejecting and self-healing. Simple procedures, with minimalprotection against surface contamination by adsorbed materials or byparticles, can lead to surprisingly low levels of defects in the finalstructures. The procedure can be conducted at atmospheric pressure, inan unprotected laboratory atmosphere. Thus, microcontact printing isespecially useful in laboratories that do not have routine access to theequipment normally used in microfabrication, or for which the capitalcost of equipment is a serious concern. Third, the patternedself-assembled monolayers can be designed to act as resists with anumber of wet-chemical etchants.

Working with liquid etchants suffers from the disadvantages of handlingsolvents and disposing of wastes, but also enjoys substantialadvantages: a high degree of control over contamination of surfaces;reduced damage to the substrate from energetic interactions with atomsor ions; the ability to manipulate complex and sensitive organicfunctionalities. Because the self-assembled monolayers are only 1-3 nmthick, there is little loss in edge definition due to the thickness ofthe resist; the major determinants of edge resolution seem to be thefidelity of the contact printing and the anisotropy of etching theunderlying metal. In the current best cases, features of size 0.2 μm canbe fabricated; edge resolution in systems showing this resolution infeature size is less than 50 nm.

In the prior art, a gold film 5 to 2000 nanometers thick is typicallysupported on a titanium-primed Si/SiO₂ wafer or glass sheet. Thetitanium serves as an adhesion promoter between gold and the support.However, the silicon wafer is rigid, brittle, and cannot transmit light;These silicon wafers are also not suitable for a large-scale, continuousprinting process, such as in letterpress, gravure, offset, and screenprinting (see Printing Fundamentals, A. Glassman, Ed. (Tappi PressAtlanta, Ga. 1981); Encyclopedia Britannica, vol. 26, pp. 76-92, 110-111(Encyclopedia Brittanica, Inc. 1991)). In addition, silicon must betreated in a separate step with an adhesion promoter such as Cr or Ti,or Au will not adequately adhere, preventing formation of a stable andwell-ordered self-assembling monolayer. Finally, silicon is opaque, soany diffraction pattern obtained must be created with reflected, nottransmitted light. What is needed is an easy, efficient and simplemethod of contact printing on an optically transparent, flexiblesubstrate, that is amenable to continuous processing.

SUMMARY OF THE INVENTION

The present invention comprises methods of contact printing ofpatterned, self-assembling monolayers of alkanethiolates, carboxylicacids, hydroxamic acids, and phosphonic acids on metallizedthermoplastic films, the compositions produced thereby, and the use ofthese compositions.

Patterned self-assembling monolayers allow for the controlled placementof fluids thereon which can contain a chemically reactive, indicatorfunctionality. The optical sensing devices produced thereby when thefilm is exposed to an analyte and light, can produce optical diffractionpatterns which differ depending on the reaction of the self-assemblingmonolayer with the analyte of interest. The light can be in the visiblespectrum, and be either reflected from the film, or transmitted throughit, and the analyte can be any compound reacting with theself-assembling monolayer. The present invention also provides aflexible support for a self-assembling monolayer on gold or othersuitable metal.

The present invention includes a support for a self-assembling monolayeron gold or other suitable material which does not require an adhesionpromoter for the formation of a well-ordered self-assembling monolayer.The present invention also provides a support for a self-assemblingmonolayer on gold or other material which is suitable for continuous,rather than batch, fabrication. Finally the present invention provides alow-cost, disposable sensor which can be mass produced.

These and other objects, features and advantages of the presentinvention will become apparent after a review of the following detaileddescription of the disclosed embodiments.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of contact printing of self-assembling monolayers.A polydimethylsiloxane (PDMS; silicone elastomer 184; Dow Corning Corp.,Midland, Mich.) is polymerized on a silicone master containing apre-determined pattern. The PDMS is peeled away from the master, andthen exposed to a solution containing HS(CH₂)₁₅ CH₃. The alkane-thiolcoated stamp is then stamped onto the gold-coated substrate. Then, thesurface of the substrate is exposed to a solution containing a differentalkane-thiol such as HS(CH₂)₁₁ OH.

FIG. 2 is an atomic force microscopy image of evaporated gold on MYLAR®,purchased from Courtaulds Performance Films (Canoga Park, Calif.). Theaverage roughness of the gold layer is 3-4 nanometers, with maximumroughness of 9 nanometers.

FIGS. 3a, 3b and 3c are atomic force microscopy images of a hydrophilicself-assembling monolayer circle of 16 mercaptohexadecanoic acids, asdescribed in Example 1. FIG. 3a is a topography image, FIG. 3b is alateral force image, and FIG. 3c is a three-dimensional graphic of atopography image.

FIG. 4 is a field emission secondary electron microscope image of 10micron-diameter circles of hydrophilic self-assembling monolayers formedby printing of 16-mercaptohexadecanoic acid, as described in Example 1,below.

FIG. 5a is an optical photomicrograph at 300× magnification of 10micron-diameter circles of hydrophilic self-assembling monolayers formedby printing of 16-mercaptohexadecanoic acid, as described in Example 1,below, and after exposure to a high surface energy, curable, opticaladhesive. The adhesive was cured by ultraviolet light (UV) exposure.

FIG. 5b is a photograph of the diffraction pattern formed by visiblelight shown through the self-assembling monolayer pattern described byFIG. 5a.

FIG. 6 is a field emission secondary electron micrograph image of 10micron-diameter circles formed by printing of self-assembledphotocurable polymers on hydrophilic self-assembling monolayers.

FIGS. 7a and 7b are field emission secondary electron micrographs of 1.5micron diameter circles formed of self-assembling photocurable polymerson hydrophilic self-assembling monolayers, printed as described inExample 1.

DETAILED DESCRIPTION

The present invention provides methods of contact printing of patterned,self-assembling monolayers of alkanethiolates, carboxylic acids,hydroxamic acids, and phosphonic acids on metallized polymer films,desirably thermoplastic polymer films, the compositions producedthereby, and the use of these compositions. Patterned self-assemblingmonolayers allow for the controlled placement of fluids thereon whichcan contain a chemically reactive, indicator functionality. The term"patterned self-assembling monolayers thereon" as used herein means theself-assembling monolayers in any pattern on the metallized polymerfilms including a solid pattern.

In one embodiment, optical sensing devices can be produced according tothe present invention. When the film with the self-assembling monolayersthereon is exposed to an analyte that is capable of reacting with theself-assembling monolayer, the film will produce optical diffractionpatterns which differ depending on the reaction of the self-assemblingmonolayer with the analyte of interest. The liquid may be a high surfacetension fluid such as water. The light can be in the visible spectrum,and be either reflected from the film, or transmitted through it, andthe analyte can be any compound reacting with the self-assemblingmonolayer.

Self-assembled monolayers of organic compounds on inorganic or metalsurfaces are becoming increasingly important in many areas of materialsscience. Although there are many different systems of self-assemblingmonolayers based on different organic components and supports, desiredsystems are those of alkanethiolates, HS(CH₂)_(n) R, on gold films.Typically, a gold film, 5 to 2000 nm thick, is supported on atitanium-primed Si/SiO₂ wafer or glass sheet. The titanium serves as anadhesion promoter between gold and the support. The alkanethiolschemisorb on the gold surface from a solution in which the gold film isimmersed, add form absorbed alkanethiolates with loss of hydrogen.Absorption can also occur from the vapor. Self-assembling monolayersformed on gold from long-chain alkanethiolates of structure X(CH₂)_(n)Y(CH₂)_(m) S are highly ordered and can be considered as crystalline orquasi-crystalline molecular arrays. A wide variety of organic functionalgroups (X,Y) can be incorporated into the surface or interior of themonolayer.

Self-assembling monolayers can therefore be tailored to provide a widevariety of material properties: wettability and protection againstcorrosion by chemical etchants are especially relevant to μCP.

FIG. 1 outlines the procedure used for microcontact printing. Anelastomeric stamp is used to transfer alkanethiol "ink" to a goldsurface by contact; if the stamp is patterned, a patternedself-assembling monolayer forms. The stamp is fabricated by castingpolydimethylsiloxane (PDMS) on a master having the desired pattern.Masters are prepared using standard photolithographic techniques, orconstructed from existing materials having microscale surface features.

In a typical experimental procedure, a photolithographically producedmaster is placed in a glass or plastic Petri dish, and a 10:1 ratio (w:wor v:v) mixture or SYLGARD® silicone elastomer 184 and SYLGARD siliconeelastomer 184 curing agent (Dow Corning Corporation) is poured over it.The elastomer is allowed to sit for approximately 30 minutes at roomtemperature and pressure to degas, then cured for 1-2 hours at 60° C.,and gently peeled from the master. "Inking" of the elastomeric stamp isaccomplished by exposing the stamp to a 0.1 to 1.0 mM solution ofalkanethiol in anhydrous ethanol, either by pouring the solution overthe surface of the stamp, or by rubbing the stamp gently with a Q-TIP®that has been saturated with the inking solution. The stamp is allowedto dry until no liquid is visible by eye on the surface of the stamp(typically about 60 seconds), either under ambient conditions, or byexposure to a stream of nitrogen gas. Following inking, the stamp isapplied (typically by hand) to a gold surface. Very light hand pressureis used to aid in complete contact between the stamp and the surface.The stamp is then gently peeled from the surface. Following removal ofthe stamp, the surface is washed of excess thiol and the patterned goldsurface can be subjected to chemical etchants (see below) thatselectively remove underivatized areas of the gold surface, and ifdesired, the underlying support(s). Alternatively, furtherderivatization of unstamped areas can be accomplished, either by using asecond stamp, or by washing the entire surface with a differentalkanethiol.

The elastomeric character of the stamp is essential to the success ofthe process. Polydimethylsiloxane (PDMS), when cured, is sufficientlyelastomeric to allow good conformal contact of the stamp and thesurface, even for surfaces with significant relief; this contact isessential for efficient contact transfer of the alkanethiol "ink" to thegold film. The elastomeric properties of PDMS are also important whenthe stamp is removed from the master: if the stamp were rigid (as is themaster) it would be difficult to separate the stamp and master aftercuring without damaging one of the two substrates. PDMS is alsosufficiently rigid to retain its shape, even for features withsub-micron dimensions: we have successfully generated patterns withlines as small as 200 nm in width. The surface of PDMS has a lowinterfacial free energy (y=22.1 dynes/cm), and the stamp does not adhereto the gold film. The stamp is durable: we have used the same stamp upto 100 times over a period of several months without significantdegradation in performance. The polymeric nature of PDMS also plays acritical role in the inking procedure, by enabling the stamp to absorbthe alkanethiol ink by swelling.

Microcontact printing on gold surfaces can be conducted with a varietyof alkanethiol "inks". Alkanethiols that do not undergo reactivespreading (after application to the gold film) are required forformation of small features with high resolution. For stamping in air,one can use autophobic alkanethiols such as hexadecanethiol.Microcontact printing of other non-autophobic alkanethiols, for example,HS(CH₂)₁₅ COOH, can be conducted by stamping under a liquid such aswater. Patterned self-assembling monolayers of alkanethiols on goldprovide excellent resist character with a number of wet-chemicaletchants.

In one embodiment of the present invention, the self-assemblingmonolayer is formed of a carboxy-terminated alkane thiol stamped with apatterned elastomeric stamp onto a gold-surfaced thermoplastic film suchas MYLAR®. The alkanethiol is inked with a solution of alkanethiol inethanol, dried, and brought into contact with a surface of gold. Thealkanethiol is transferred to the surface only at those regions wherethe stamp contacts the surface, producing a pattern of self-assemblingmonolayer which is defined by the pattern of the stamp. Optionally,areas of unmodified gold surface next to the stamped areas can berendered hydrophobic by reaction with a methyl-terminated alkane thiol.

A more detailed description of the methods and compositions of thepresent invention follows. All publications cited herein areincorporated by reference in their entirety.

Any thermoplastic film upon which a metal substrate can be deposited issuitable for the present invention. These include, but are not limitedto polymers such as: polyethylene-terephthalate (MYLAR®),acrylonitrilebutadiene-styrene, acrylonitrile-methyl acrylate copolymer,cellophane, cellulosic polymers such as ethyl cellulose, celluloseacetate, cellulose acetate butyrate, cellulose propionate, cellulosetriacetate, cellulose triacetate, polyethylene, polyethylene-vinylacetate copolymers, ionomers (ethylene polymers) polyethylene-nyloncopolymers, polypropylene, methyl pentene polymers, polyvinyl fluoride,and aromatic polysulfones. Preferably, the plastic film has an opticaltransparency of greater than 80%. Other suitable thermoplastics andsuppliers may be found, for example, in reference works such as theModern Plastics Encyclopedia (McGraw-Hill Publishing Co., New York1923-1996).

In one embodiment of the invention, the thermoplastic film with themetal coating thereon has an optical transparency of betweenapproximately 5% and 95%. A more desired optical transparency for thethermoplastic film used in the present invention is betweenapproximately 20% and 80%. In a desired embodiment of the presentinvention, the thermoplastic film has at least an approximately 80%optical transparency, and the thickness of the metal coating is such asto maintain an optical transparency greater than about 20%, so thatdiffraction patterns can be produced by either reflected or transmittedlight. This corresponds to a metal coating thickness of about 20 nm.However, in other embodiments of the invention, the gold thickness maybe between approximately 1 nm and 1000 nm.

The preferred metal for deposition on the film is gold. However, silver,aluminum, copper, iron, zirconium, platinum and nickel, as well as othermetals, may be used. Preferred metals are ones that do not form oxides,and thus assist in the formation of more predictable self-assemblingmonolayers.

In principle, any surface with corrugations of appropriate size could beused as masters. The process of microcontact printing starts with anappropriate relief structure, from which an elastomeric stamp is cast.This `master` template may be generated photolithographically, or byother procedures, such as commercially available diffraction gratings.In one embodiment, the stamp may be made from polydimethylsiloxane.

In one embodiment of the present invention, the self-assemblingmonolayer has the following general formula:

    X--R--Y

X is reactive with metal or metal oxide. For example, X may beasymmetrical or symmetrical disulfide (--R'SSR, --RSSR), sulfide(--R'SR, --RSR), diselenide (--R'Se--SeR), selenide (--R'SeR, --RSeR),thiol (--SH), nitrile (--CN), isonitrile, nitro (--NO₂), selenol(--SeH), trivalent phosphorous compounds, isothiocyanate, xanthate,thiocarbamate, phosphine, thioacid or dithioacid, carboxylic acids,hydroxylic acids, and hydroxamic acids.

R and R' are hydrocarbon chains which may optionally be interrupted byhetero atoms and which are preferably non-branched for the sake ofoptimum dense packing. At room temperature, R is greater than or equalto seven carbon atoms in length, in order to overcome naturalrandomizing of the self-assembling monolayer. At colder temperatures, Rmay be shorter. In a preferred embodiment, R is --(CH₂)_(n) -- where nis between 10 and 12, inclusive. The carbon chain may optionally beperfluorinated.

Y may have any surface property of interest. For example, Y could be anyamong the great number of groups used for immobilization in liquidchromatography techniques, such as hydroxy, carboxyl, amino, aldehyde,hydrazide, carbonyl, epoxy, or vinyl groups. Examples of sensing layermaterials are set forth in "Patterning Self-Assembled Monolayers UsingMicrocontact Printing: A New Technology for Biosensors?," by MilanMrksich and George M. Whitesides, published in TIBTECH, June, 1995 (Vol.13), pp. 228-235, hereby incorporated by reference.

Self assembling monolayers of alkyl phosphonic, hydroxamic, andcarboxylic acids may also be useful for the methods and compositions ofthe present invention. Since alkanethiols do not adsorb to the surfacesof many metal oxides, carboxylic acids, phosphonic acids, and hydroxamicacids may be preferred for X for those metal oxides. See J. P. Folkers,G. M. Whitesides, et al., Langmuir, 1995, vol. 11, pp. 813-824.

R may also be of the form (CH₂)_(a) --Z--(CH₂)_(b), where a≧0, b≧7, andZ is any chemical functionality of interest, such as sulfones, urea,lactam, etc.

The stamp may be applied in air, or under a fluid such as water toprevent excess diffusion of the alkanethiol. For large-scale orcontinuous printing processes, it is most desirable to print in air,since shorter contact times are desirable for those processes.

In one embodiment of the present invention, the pattern is formed on themetallized thermoplastic polymer with the self-assembling monolayer. Inanother embodiment of the present invention, the relief of the patternis formed with the self-assembling monolayer. After the stampingprocess, the metallized areas on the plastic may optionally bepassivated, for example, with a methyl-terminated self-assemblingmonolayer such as hexadecylmercaptan.

This invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations upon thescope thereof. On the contrary, it is to be clearly understood thatresort may be had to various other embodiments, modifications, andequivalents thereof, which, after reading the description herein, maysuggest themselves to those skilled in the art without departing fromthe spirit of the present invention.

EXAMPLE 1 Printing of Gold-Coated MYLAR® (polyethylene terephthalate)with Patterns of 16-mercaptohexadecanoic acid and hexadecanethiol

Patterns of gold-coated MYLAR® (polyethylene terephthalate) were printedwith patterns of 16 mercaptohexadecanoic acid and hexadecanethiol, asshown in FIG. 1, and described below.

MYLAR® film modified with a plasma deposited gold topcoat was obtainedfrom Courtaulds Performance Films (21034 Osborne Street, Canoga Park,Calif. 91304). An atomic force microscopy image of this MYLAR film isshown in FIG. 2. Polymer film thickness between 2 and 7 mils and goldtopcoats producing a surface resistance of 65 ohms per square centimeterwith a visible light transmittance between 20% and 65% were used.

Patterns of hydrophilic, carboxy-terminated alkane thiols were stampedonto gold-coated film using 16-mercaptohexadecanoic acid by thefollowing method. An exposed and developed photoresist pattern of 10micron diameter circles on a silicon wafer was used as the master.Polydimethylsiloxane (PDMS; silicone elastomer 184; Dow Corning Co.,Midland, Mich.), was polymerized on a master to produce a stamp with tenmicron-diameter circles spaced five microns apart. The stamp was inkedby exposure to a solution (1 to 10 mM in ethanol) of16-mercaptohexadecanoic acid, and allowed to air-dry. The substrate wascontacted with the stamp for 50 seconds and washed for 2 to 4 secondswith a solution of hexadecanethiol (1 to 10 mM in ethanol). Thesubstrate was finally washed for 10 seconds in ethanol and dried in astream of nitrogen. The results of this printing are shown in FIG. 3 andFIG. 4 for the 10 micron diameter circles of the carboxylic acidterminated self-assembling monolayer.

These hydrophilic self-assembling monolayer circles allow for selectiveplacement of high surface tension fluids such as water, triethyleneglycol, or ultraviolet light curable urethane acrylic adhesives. Theseliquids can contain dissolved and suspended reagents that reactchemically or physically with targeted analytes, thus making the coatedplastic film a collection of 10 micron microreactors suitable for lowcost, disposable chemical sensors. An example of such a device is shownin FIG. 5a, FIG. 6, and FIGS. 7a and 7b.

Diffraction of visible light was shown with these compositions. Bothreflected and transmitted diffraction patterns were observed when using5 mW, 670 nM laser illumination. FIG. 5b is a photograph of thediffraction pattern formed by visible light shown through theself-assembling monolayer pattern of FIG. 5a. Rainbow diffraction colorswere observed with transmitted white light.

EXAMPLE 2 Printing of Aluminum-coated MYLAR® with Patterns of16-carboxy-hexadecanoic Acid and hexadecanecarboxylate

The procedure of Example 1 was followed for 100 gauge aluminum-coatedMYLAR® with 35% visible light transmission, substituting the 1,16-dihydroxamic acid of hexadecane and 1-hexadecane hydroxamic acid forthe hydrophilic and hydrophobic thiols, respectively, of Example 1.Diffraction of visible light occurred. Both reflected and transmitteddiffraction patterns were observed when using 5 mW, 670 nM laserillumination. Rainbow diffraction colors were observed with transmittedwhite light.

EXAMPLE 3 Comparison of Gold-Coated MYLAR® with Gold-Coated SiliconWafers.

Gold films (100 angstroms to 1 micrometer) were deposited by electronbeam evaporation on silicone wafers that had been primed with titanium(5-50 angstroms) to promote adhesion between silicon and gold. Stampingon both gold-coated film and gold-coated silicon wafers was performed asin Example 1.

Measurement of Contact Angles

Contact angles were measured on a Rame-Hart Model 100 goniometer at roomtemperature and ambient humidity. Water for contact angles was deionizedand distilled in a glass and Teflon apparatus. Advancing and recedingcontact angles were measured on both sides of at least three drops ofeach liquid per slide; data in the figures represents the average ofthese measurements. The following method was used for measuring contactangles: A drop approximately 1-2 microliters in volume was grown on theend of a pipette tip (Micro-Electrapette syringe; Matrix Technologies;Lowell, Mass.). The tip was then lowered to the surface until the dropcame in contact with the surface. The drop was advanced by slowlyincreasing the volume of the drop (rate approximately 1microliter/second). Advancing contact angles of water were measuredimmediately after the front of the drop had smoothly moved a shortdistance across the surface. Receding angles were taken after the drophad smoothly retreated across the surface by decreasing the volume ofthe drop.

X-ray Photoelectron Spectroscopy (XPS)

X-ray photoelectron spectra were collected on a Surface Science SSX-100spectrometer using a monochromatized A1 K-alpha source (hv=1486.6electron volts). The spectra were recorded using a spot size of 600micrometers and a pass energy on the detector of 50 electron volts(acquisition time for one scan was approximately 1.5 minutes). For themonolayers, spectra were collected for carbon and oxygen using the 1speaks at 285 and 530 eV, respectively; the binding energies for elementsin the monolayer were referenced to the peak due to hydrocarbon in the C1s region, for which we fixed the binding energy at 284.6 eV. Spectrafor the solid hydroxamic acid were collected using an electron flood gunof 4.5 eV to dissipate charge in the sample. The following signals wereused for the substrates; Al 2p at 73 eV for Al(0), and at 75 eV forAl(III). The binding energies for the substrates were not standardizedto a reference sample. All spectra were fitted using an 80% Gaussian/20%Lorentzian peak shape and a Shirley background subtraction. See J. P.Folkers, G. M. Whitesides, et al., Langmuir, vol. 11, no. 3, pp. 813-824(1995).

Condensation Figures

Condensation figures (CFs) are arrays of liquid drops that form uponcondensation of vapor onto a solid surface. The examination ofcondensation figures has historically been used as a method tocharacterize the degree of contamination on an otherwise homogeneoussurface. One is able to impose a pattern on arrays of condensed drops bypatterning the surface underlying them into regions of differentsolid-vapor interfacial free energy and to characterize the patternedCFs by photomicroscopy and optical diffraction. It can be demonstratedthat appropriately patterned CFs can be used as optical diffractiongratings and that examination of the diffraction patterns provides botha rapid, nondestructive method for characterizing patternedself-assembling monolayers and an approach to sensing the environment.Because the form of the CFs--that is, the size, density, anddistribution of the drops--is sensitive to environmental factors, CFs ofappropriate size and pattern diffract light and can be used as sensors.This principle is demonstrated by correlating the temperature of asubstrate patterned into hydrophobic and hydrophilic regions, in anatmosphere of constant relative humidity, with the intensity of lightdiffracted from CFs on these regions.

Appropriate patterns are formed from self-assembled monolayers(self-assembling monolayers) on gold by using combinations ofhexadecanethiol [CH₃ ((CH₂)₁₅ SH], 16-mercaptohexadecanoic acid[HS(CH₂)₁₄ COOH], and 11-mercaptoundecanol [HS(CH)₁₁ OH]. Severaltechniques are now available for preparing patterns of two or moreself-assembling monolayers having 0.1- to 10-μm dimensions.

At 20° C., an incident beam of light from a laser (helium-neon laser,wavelength=632.8 nm) produced a single transmitted spot because no waterhad condensed on the surface, and the transmittance of the regionscovered with different self-assembling monolayers were effectivelyindistinguishable. As the surface was exposed to warm, moist air,droplets of water condensed preferentially on the hydrophilic regions.Diffraction patterns appeared in the light transmitted from the surface.Under these conditions, light was transmitted coherently from theregions where no water had condensed and was scattered by the regionswhere water had condensed. The condensation figures disappeared withinseveral seconds as the water droplets which condensed on theself-assembling monolayers evaporated.

The ability to form condensation figures can be ascertained by therelative contact angles of water on the hydrophobic and hydrophilicself-assembling monolayers. Unpatterned monolayers of the appropriatethiol were prepared by immersion of the substrate in a dilute solutionfor one hour, followed by rinsing with ethanol and air drying.

                  TABLE I                                                         ______________________________________                                        Comparison of Gold-Coated MYLAR ® with Gold-Coated                          Silicon Wafers: Reactions of ω-functionalized alkane-thiols                        XPS          Water Contact                                                                               Results Angles                                   % C        % O     % Au                                            ______________________________________                                        Untreated Controls                                                              Au on MYLAR ®  47.4 3.9 48.8                                              Au on MYLAR ®* 42.6 ND 57.4                                               (2nd sample)                                                                  Au on SiO.sub.X ** 47.5 ND 52.5                                               React with                                                                    CH.sub.3 (CH.sub.2).sub.15 SH                                                 Au on SiO.sub.X 72.7 ND 27.3                                                   72.7 ND 27.3                                                                 Au on MYLAR 71.4 ND 28.6                                                       71.8 ND 28.2                                                                 React with                                                                    HOC(O)CH.sub.2).sub.14 SH                                                     Au on SiO.sub.X 64.9 8.5 26.6                                                  65.4 8.2 26.4                                                                Au on MYLAR 68.9 7.2 23.9                                                   ______________________________________                                         *Gold-coated MYLAR substrate                                                  **Silicon Oxide Substrate                                                     "ND" means "not detected", i.e., less than 0.2 atompercent.              

Condensation Figures [Science, Vol. 263, 60 (1994), incorporated hereinby reference] with equivalent optical diffraction can be formed onAu:MYLAR®, relative to known art with Au:SiOx. The chemistry ofalkanethiols reacting with Au:MYLAR is similar to that reported in theliterature for Au:SiOx.

EXAMPLE 4 Comparison of Aluminum/AlO_(x) -Coated MYLAR® with Al/AlO_(x)-Coated Silicon Wafers; Reaction of the hydroxamic acid CH₃ --(CH₂)₁₆--CONH(OH)

Using the procedures of Example 2, unpatterned monolayers of theappropriate hydroxamic acid were prepared by immersion of the substratein a dilute solution for one hour, followed by rinsing with ethanol andair drying. The results are set forth in Table II, below.

                  TABLE II                                                        ______________________________________                                        Comparison of Aluminum/AlO.sub.X Coated MYLAR ® with                        Al/Al/O.sub.X Coated Silicon Wafers: Reaction of                              the Hydroxamic Acid CH.sub.3 (CH.sub.2).sub.16 CONH(OH)                     ______________________________________                                                         XPS Results                                                  Untreated Controls % C    % O                                                 ______________________________________                                          AlO.sub.X on MYLAR ® 28.9 41.2                                            (repeat analysis) 30.3 38.6                                                   AlO.sub.X on SiO.sub.X 49.7 24.6                                               48.7 24.3                                                                  ______________________________________                                        Water Contact                                                                   Angles Untreated                                                              Controls                                                                      AlO.sub.X on MYLAR ® 68-74°                                        AlO.sub.X on SiO.sub.X 74-78°                                          Reacted with Hydroxamic Acid                                                  Compound for 10 minutes                                                       AlO.sub.X on MYLAR ® 90-92°                                        AlO.sub.X on SiO.sub.X 90-92°                                        ______________________________________                                    

Condensation figures [per method of Science, Vol. 263, p. 60 (1994),incorporated herein by reference] with equivalent optical diffractioncan be formed via contact printing.

Al-coated, optical grade MYLAR® shows similar abilities to Al-coatedsilicon in promoting contact printing of self-assembling monolayers.

EXAMPLE 5 Self-Assenbled Photocitrable Polymers on HydrophilicSelf-Assembling Monolayers.

FIG. 6 is a field emission secondary electron microscopy image of 10micron-diameter self-assembled photocurable polymers on hydrophilicself-assembling monolayers.

Those skilled in the art will now see that certain modifications can bemade to the invention herein disclosed with respect to the illustratedembodiments, without departing from the spirit of the instant invention.And while the invention has been described above with respect to thepreferred embodiments, it will be understood that the invention isadapted to numerous rearrangements, modifications, and alterations, allsuch arrangements, modifications, and alterations are intended to bewithin the scope of the appended claims.

We claim:
 1. A film with patterned self-assembling monolayers thereoncomprising:a polymer film having an optical transparency between 5% and95% coated with metal; and a self-assembling monolayer printed onto themetal coating of the polymer film, wherein the self-assembling monolayeris printed in a first, non-diffracting pattern such that when an analytebinds to the polymer film, the polymer film diffracts transmitted lightto form a second pattern, wherein the second pattern is a diffractionpattern.
 2. The film of claim 1, wherein the metal is selected from thegroup consisting of gold, silver, nickel, platinum, aluminum, iron,copper, or zirconium.
 3. The film of claim 1, wherein the metal is gold.4. The film of claim 3, wherein the gold coating is betweenapproximately 1 nanometer and 1000 nanometers in thickness.
 5. The filmof claim 1, wherein the polymer film is polyethylene-terephthalate,acrylonitrile-butadiene-styrene, acrylonitrile-methyl acrylatecopolymer, cellophane, cellulosic polymers such as ethyl cellulose,cellulose acetate, cellulose acetate butyrate, cellulose propionate,cellulose triacetate, polyethylene, polyethylene-vinyl acetatecopolymers, ionomers (ethylene polymers) polyethylene-nylon copolymers,polypropylene, methyl pentene polymers, polyvinyl fluoride, and aromaticpolysulfones.
 6. The film of claim 4, wherein the polymer film ispolyethylene-terephthalate.
 7. The film of claim 1, wherein the polymerfilm is optically transparent.
 8. The film of claim 1, wherein thepolymer film has an optical transparency between approximately 20% and80%.
 9. The film of claim 1, wherein the self-assembling monolayer isformed from compounds with the following general formula:

    X--R--Y

wherein: X is reactive with the metal or metal oxide on the polymerfilm; R is a hydrocarbon chain; and Y is a compound with any property ofinterest.
 10. The film of claim 9, wherein:X is an asymmetrical orsymmetrical disulfide (--R'SSR, --RSSR), sulfide (--R'SR, --RSR),diselenide (--R'Se--SeR), selenide (R'SeR, --RSeR), thiol (--SH),nitrile (--CN), isonitrile, nitro (--NO₂), selenol (--SeH), trivalentphosphorous compounds, isothiocyanate, xanthate, thiocarbamate,phosphine, thioacid or dithioacid, carboxylic acids, hydroxylic acids,and hydroxamic acids; R and R' are hydrocarbon chains which mayoptionally be interrupted by hetero atoms, and which may optionally beperfluorinated, and which are preferably non-branched; and Y is selectedfrom the group consisting of hydroxy, carboxyl, amino, aldehyde,hydrazide, carbonyl, epoxy, or vinyl groups.
 11. The film of claim 9,wherein R is greater than 7 carbon atoms in length.
 12. The film ofclaim 9, wherein R is a compound of the form (CH₂)_(a) --Z--(CH₂)_(b),wherein a≧0, b≧7, and Z is any chemical functionality of interest. 13.The film of claim 12, wherein Z is selected from the group consisting ofsulfones, lactams, and urea.
 14. The film of claim 1, wherein thepolymer film is stamped with a first self-assembling monolayer and asecond self-assembling monolayer, and wherein each self-assemblingmonolayer has different chemical properties.
 15. The film of claim 14,wherein the first self-assembling monolayer is hydrophobic and thesecond self-assembling monolayer is hydrophilic.
 16. A film withpatterned self-assembling monolayers thereon comprsing:a polymer filmcoated with metal; and a self-assembling monolayer printed onto themetal coating of the polymer film, wherein the self-assembling monolayeris printed in a pattern; wherein the polymer film ispolyethylene-terephthalate.
 17. The film of claim 16, wherein the metalis selected from the group consisting of gold, silver, nickel, platinum,aluminum, iron, copper, and zircomum.
 18. The film of claim 16, whereinthe metal is gold.
 19. The film of claim 18, wherein the gold coating isbetween approximately 1 nanometer and 1000 nanometers in thickness. 20.The film of claim 16, wherein the polymer film is optically transparent.21. The film of claim 16, wherein the polymer film has an opticaltransparency between 5% and 95%.
 22. The film of claim 16, wherein thepolymer film has an optical transparency between approximately 20% and80%.
 23. The film of claim 16, wherein the self-assembling monolayer isformed from compounds with the following general formula:

    X--R--Y

wherein: X is reactive with the metal or metal oxide on the polymerfilm; R is a hydrocarbon chain; and Y is a compound with any property ofinterest.
 24. The film of claim 23, wherein:X is an asymmetrical orsymmetrical disulfide (--R'SSR, --RSSR), sulfide (--R'SR, --RSR),diselenide (--R'Se--SeR), selenide (R'SeR, --RSeR), thiol (--SH),nitrile (--CN), isonitrile, nitro (--NO₂), selenol (--SeH), trivalentphosphorous compounds, isothiocyanate, xanthate, thiocarbamate,phosphine, thioacid or dithioacid, carboxylic acids, hydroxylic acids,and hydroxamic acids; R and R' are hydrocarbon chains which mayoptionally be interrupted by hetero atoms, and which may optionally beperfluorinated, and which are preferably non-branched; and Y is selectedfrom the group consisting of hydroxy, carboxyl, amino, aldehyde,hydrazide, carbonyl, epoxy, or vinyl groups.
 25. The film of claim 23,wherein R is greater than 7 carbon atoms in length.
 26. The film ofclaim 23, wherein R is a compound of the form (CH₂)_(a) --Z--(CH₂)_(b),wherein a≧0, b≧7, and Z is any chemical functionality of interest. 27.The film of claim 26, wherein Z is selected from the group consisting ofsulfones, lactams, and urea.
 28. The film of claim 16, wherein thepolymer film is stamped with a first self-assembling monolayer and asecond self-assembling monolayer, and wherein each self-assemblingmonolayer has different chemical properties.
 29. The film of claim 28,wherein the first self-assembling monolayer is hydrophobic and thesecond self-assembling monolayer is hydrophilic.